Why do people suffer from back pain?

Why do people suffer from back pain?

As part of the evolutionary cycle, when humans adopted the erect posture, a change occurred in the way that body weight was transmitted to the ground.

Humans turned biped (two-legged) and so necessarily had to transmit body weight via the spine to the hip joints and the lower limbs. Unfortunately, the lumbar spine did not evolve at the same pace and has become the commonest area of the spine to be subjected to degenerative processes, also known as spondylitis. So taking care of your back by means of proper posture, spine exercises and avoiding strain assumes greater importance because of the evolutionary disadvantage.

I read it here